| 南京北郊PM2.5中有机组分的吸光性质及来源 |
| 摘要点击 2370 全文点击 732 投稿时间：2020-06-22 修订日期：2020-08-26 |
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| 中文关键词 棕碳(BrC) 化学组分 吸光性质 时间变化 来源 |
| 英文关键词 brown carbon(BrC) chemical component light-absorbing property temporal variation source |
| 作者 | 单位 | E-mail | | 尚玥 | 南京信息工程大学环境科学与工程学院, 大气环境与装备技术协同创新中心, 江苏省大气环境监测与污染控制高技术研究重点实验室, 南京 210044 | 791594311@qq.com | | 余欢 | 中国地质大学(武汉)环境学院大气科学系, 武汉 430074 | | | 茅宇豪 | 南京信息工程大学环境科学与工程学院, 大气环境与装备技术协同创新中心, 江苏省大气环境监测与污染控制高技术研究重点实验室, 南京 210044 | | | 王成 | 南京信息工程大学环境科学与工程学院, 大气环境与装备技术协同创新中心, 江苏省大气环境监测与污染控制高技术研究重点实验室, 南京 210044 | wangcheng118@163.com | | 谢鸣捷 | 南京信息工程大学环境科学与工程学院, 大气环境与装备技术协同创新中心, 江苏省大气环境监测与污染控制高技术研究重点实验室, 南京 210044 | mingjie.xie@nuist.edu.cn |
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| 中文摘要 |
| 对南京北郊2018年9月~2019年9月PM2.5中有机组分的吸光性质进行了研究，并利用PM2.5化学组成及主成分分析法分析该地区吸光性有机碳（棕碳，brown carbon，BrC）的主要来源.结果表明，水溶性有机碳（water-soluble organic carbon，WSOC）和甲醇可提取有机碳（methanol extractable organic carbon，MEOC）在365 nm处光吸收系数（Abs365，w和Abs365，m）的平均值分别为（3.22±2.18）Mm-1和（7.69±4.93）Mm-1.Abs365，w和Abs365，m分别与WSOC（r=0.72，P<0.01）和MEOC（r=0.62，P=0.04）的质量浓度显著相关，均表现为冬高夏低，夜高昼低的时间变化特征.这可归结于冬季和夜间的气象特征（例如边界层高度降低和大气稳定度升高）、冬季一次源排放的增加以及夏季和白天更强的"光漂白作用".Abs365，m/Abs365，w的年均值（2.60±0.92）远高于MEOC/WSOC（质量浓度比值，1.37±0.30），表明MEOC中非水溶性组分的吸光作用更强，在BrC的吸光作用中占主导地位.WSOC、MEOC、Abs365，m和K+均未表现出强相关性（r<0.60），因此生物质燃烧不是该地区BrC的主要一次来源.WSOC和MEOC质量吸收效率（MAE365，w和MAE365，m）及其比值（MAE365，m/MAE365，w）的季节变化和Abs365相同.MEOC中非水溶性组分的MAE365［（4.10±5.15）m2·g-1］分别是MAE365，w和MAE365，m的6.0和2.9倍，支持BrC的吸光作用受非水溶性有机组分主导这一推断.和WSOC的埃氏吸收指数（ÅWSOC）相比，MEOC的埃氏吸收指数（ÅMEOC）随时间变化更显著，这可能与非水溶性吸光组分排放的季节变化有关.主成分分析结果显示，本研究PM2.5中有机组分的吸光作用主要来源于二次形成过程和人为活动相关的一次排放，而不是生物质燃烧. |
| 英文摘要 |
| The light absorption of organic components in PM2.5 was investigated at a suburban site in northern Nanjing from September 2018 to September 2019, and PM2.5 compositional data and principal component analysis (PCA) were used to identify the sources of light-absorbing organic carbon (brown carbon, BrC). The results showed that the average light absorption coefficients of water-soluble organic carbon (WSOC) and methanol extractable organic carbon (MEOC) were (3.22±2.18) Mm-1 (Abs365,w) and (7.69±4.93) Mm-1(Abs365,m), respectively. Significant correlations were observed between Abs365,w and mass concentrations of WSOC (r=0.72, P<0.01) and between Abs365,m and mass concentrations of MEOC (r=0.62, P=0.04). Both Abs365,w and Abs365,m exhibited seasonal variations, with higher values during winter than during summer,and higher diel variations at night than during the day. This can be attributed to meteorological characteristics during the winter and nighttime, i.e., decreased boundary layer height and increased atmospheric stability, enhanced primary emissions in winter,and stronger photobleaching effects during the summer and during the day. The annual average Abs365,m/Abs365,w ratio (2.60±0.92) was much larger than the average mass ratio of MEOC/WSOC (1.37±0.30), indicating that the water-insoluble fraction of MEOC had a stronger light absorption effect and dominated BrC absorption. No strong correlation (r<0.60) was observed between WSOC, MEOC, Abs365,m, and mass concentrations of K+, indication that biomass burning was not the main source of BrC in the study location. The mass absorption efficiency of WSOC (MAE365,w) and MEOC (MAE365,m) and their ratios (MAE365,m/MAE365,w) showed similar seasonal variations to Abs365. The average MAE365 value of the water-insoluble fraction of MEOC (4.10±5.15) m2·g-1 was 6.0 and 2.9 times higher than that of MAE365,w and MAE365,m, respectively, suggested that BrC absorption was primarily attributable to water-insoluble components. In comparison to the absorption Ångström exponent of WSOC (ÅWSOC), ÅMEOC displayed marked temporal variability, which might be related to the seasonal variation in the emission of water-insoluble chromophores. According to the PCA results, the light absorption of PM2.5 organic was mainly attributed to secondary formation and anthropogenic primary emissions rather than biomass burning. |
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